Teratomas of anterior mediastinum are rare. They are often slow growing, asymptomatic, and detected incidentally on chest imaging. Mycobacterium abscessus (M. abscessus) is an acid-fast bacillus that is classified as a pathogenic "rapid growing" non-tuberculous mycobacteria. It is an uncommon cause of human pathology, which may cause skin and soft tissue infection after skin injury following inoculation, minor trauma, and surgery. Here, we present an unusual case of benign cystic teratoma mimicking recurrent pleural effusion, which was subsequently complicated by M. abscessus infection following thoracotomy. Cystic teratoma is rare, but it needs to be considered whenever clinical and investigative work-up fails to provide a convincing diagnosis. A combined clinical, radiological, surgical, and histopathological assessment is important to arrive at the correct diagnosis. Rapidly growing mycobacteria needs to be included in the differential diagnosis of patients with non-resolving infected post-thoracotomy wound and who do not respond to broad-spectrum antibiotics.